<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .outer{
            width: 300px;
            height: 200px;
            border: 1px solid black;
            margin: 0 auto;
            transform-style: preserve-3d;
            perspective: 500px;
        }
        .inner{
            width: 300px;
            height: 200px;
            background-color: aqua;
            opacity: 0.5;
            transform: translateZ(100px);
        }
    </style>
</head>
<body>
    <div class="outer">
        <div class="inner"></div>
    </div>
</body>
</html>